1. Field of Invention
The invention relates to a paper feeder for use in an image forming apparatus, such as a copying machine, a printer, and a facsimile machine. More particularly, it relates to the paper feeder that stably feeds out paper, such as a document.
2. Description of Related Art
Conventional paper feeders that are employed in, for example, facsimile machines, include a separation roller to separate pages from a stack of documents, one by one, and a pick-up roller, disposed upstream of the separation roller in a document feeding direction, to feed out the pages in the feeding direction thereof. Typically, the separation roller and the pick-up roller are rotatably supported by a frame member.
An example of a conventional paper feeder 50 is shown in FIG. 5. FIG. 5 is a schematic, partially sectional side view of the conventional paper feeder 50. A set of documents P is stacked on a paper feed slope 51. A separation pad 52, disposed downstream of the paper feed slope 51 in the document P feeding direction (right side in FIG. 5), separates leading edges of the documents P, one by one. Disposed above the separation pad 52, is a separation roller 53. The separation roller 53 separates pages from the stack of the documents P, one by one, in cooperation with the separation pad 52, and transfers the pages of the documents P in the feeding direction thereof. The separation roller 53 is mounted on a separation roller shaft 53a, which extends through the frame member 54. The separation roller 53 is rotatably supported by the separation roller shaft 53a, in the body of the image reading device 2. Mounted on the separation roller shaft 53a, near one end of the separation roller 53, is a gear (not shown), that is engaged with an idle gear 56 (described below), to transmit the rotation of the separation roller 53 thereto.
Disposed on the document P feeding upstream side in the frame member 54 (left side in FIG. 5), is a pick-up roller 55. Similar to the separation roller 53, the pickup roller 55 transfers separated individual pages of the documents P in the feeding direction thereof. The pick-up roller 55 is rotatably supported by a pick-up roller shaft 55a in the frame member 54. Mounted on the pick-up roller shaft 55a, near one end of the pick-up roller 55, is a gear (not shown) that is engaged with the idle gear 56, to transmit the rotation of the pick-up roller 55 thereto, similar to the separation roller 53.
Between the pick-up roller 55 and the separation roller 53, the idle gear 56 is disposed in a position where the idle gear 56 is engaged with each gear mounted near the ends of the separation roller 53 and the pick-up roller 55. The idle gear 56 transmits the rotation of the separation roller 53 to the pick-up roller 55, while being engaged with the gears mounted near the separation roller 53 and the pick-up roller 55.
The idle gear 56 is rotatably supported by an idle gear shaft 56a, which is provided on the frame member 54. In FIG. 5, an outer circle of the idle gear 56 indicates an addendum circle. An inner circle of the idle gear 56 indicates a dedendum circle. A circle written in dot-dash lines between the outer and the inner circles of the idle gear 56 indicates a pitch circle of the idle gear 56.
As described above, the idle gear 56 is disposed between the pick-up roller 55 and the separation roller 53, in a position where the idle gear 56 is engaged with each gear mounted near the ends of the separation roller 53 and the pick-up roller 55. With this structure, the separation roller 53 and the pick-up roller 55 may rotate in the same direction. A top page of the documents P, may be transferred in the feeding direction thereof, by the separation roller 53, the pick-up roller 55, and the separation pad 52.
Loading a set of documents P on the paper feed slope 51 is difficult if the pick-up roller 55 makes contact with an upper surface of the paper feed slope 51. Conventionally, a hook 54a protruding upwardly from an upper portion of the frame member 54, and another hook 50a protruding downwardly from the body of the paper feeder 50 are connected by an extension spring 57. A user pulls upwardly the pick-up roller 55 to load a set of documents P on the paper feed slope 51.
As the set of documents P is loaded and the feeding thereof is started, the user moves the pick-up roller 55 down, so that the separation roller 53 and the pick-up roller 55 make contact with the top page of the documents P. Then, the separation roller 53 and the pick-up roller 55 start to rotate in the direction to feed the documents P in the feeding direction thereof.
However, with the above-described structure, the pick-up roller 55 is pulled upwardly by the extension spring 57, even after the document P feeding is started. Therefore, the pick-up roller 55 unstably makes contact with the documents P, resulting in an unstable feeding thereof.
One aspect of the invention is to provide a paper feeder that stably feeds out paper, such as a document. To achieve this aspect, the paper feeder of the invention may include a separation roller that separates a plurality of stacked documents, one by one, a pick-up roller that is disposed upstream of the separation roller in a document feeding direction, and that feeds out the documents toward the separation roller, a frame member that supports a rotating shaft for the separation roller and a rotating shaft for the pick-up roller, and a lifting member that turns the frame member in a direction away from a document positioning portion, so as to move the pick-up roller away from the document positioning portion, by transmitting a rotation of the rotating shaft for the separation roller to the frame member, when the rotating shaft for the separation roller rotates opposite to a direction to feed the documents in the document feeding direction.
In the paper feeder, after a set of the documents has been fed, the lifting member transmits the rotation of the rotating shaft for the separation roller to the frame member, as the rotating shaft for the separation roller rotates opposite to the direction to feed documents in the document feeding direction, by a predetermined amount. Accordingly, the frame member is turned in the direction away from the document positioning portion, so as to move the pick-up roller away therefrom.
In the paper feeder of the invention, the lifting member may include a frame collar that projects from an insertion portion of the rotating shaft for the separation roller in the frame member, the frame collar placing the rotating shaft for the separation roller therein, a first collar that is disposed near the frame collar and rotatably inserted over the rotating shaft for the separation roller, a second collar that is disposed near a first collar end opposite to the frame collar, and fixedly inserted over the rotating shaft for the separation roller, a first clutch member that places the frame collar and the first collar therein, wherein when the rotating shaft for the separation roller rotates in the direction to feed the documents in the document feeding direction, the first clutch member causes the frame collar and the first collar to separately and independently act, and when the rotating shaft for the separation roller rotates opposite to the direction to the document feeding direction, the first clutch member causes the frame collar and the first collar to act as one-piece, and a second clutch member that places the first collar and the second collar therein, wherein when the rotating shaft for the separation roller rotates in the direction to feed the documents in the document feeding direction, the second clutch member causes the first collar and the second collar to act as one-piece, and when the rotating shaft for the separation roller rotates opposite to the document feeding direction, the second clutch member causes the first collar and the second collar to act as one-piece, until a predetermined torque is produced on the rotating shaft for the separation roller, and the second clutch member causes the first collar and the second collar to separately and independently act, as a torque equal to or greater than the predetermined torque is produced on the rotating shaft for the separation roller, when the rotating shaft for the separation roller rotates opposite to the direction to the document feeding direction.
When the rotating shaft for the separation roller rotates in the document feeding direction, the first clutch member causes the frame collar protruding from the frame member and the first collar rotatably inserted over the rotating shaft for the separation roller to separately and independently act, and the second clutch member causes the first collar and the second collar fixed to the rotating shaft for the separation roller to act as one-piece. Accordingly, the rotating shaft for the separation roller may rotate in the direction to feed the documents in the document feeding direction. When the rotating shaft for the separation roller rotates opposite to the direction to the document feeding direction and the predetermined torque is not produced on the rotating shaft for the separation roller, the first clutch member and the second clutch member cause the frame collar, the first collar, and the second collar to act as one-piece. When the rotating shaft for the separation roller rotates opposite to the document feeding direction and the torque equal to or greater than the predetermined torque is produced on the rotating shaft for the separation roller, the first clutch member causes the frame collar and the first collar to act as one-piece and the second clutch member causes the first collar and the second collar to separately and independently act.
In the paper feeder, the first clutch member may include a bearing-type one-way clutch that allows the first collar to rotate only in the direction to feed the documents in the document feeding direction.
When the documents are fed in the document feeding direction, the rotating shaft for the separation roller may be rotated to feed the documents in document feeding direction, by the act of the bearing-type one-way clutch and the first collar separately and independently. When the frame member is turned so as to lift the pick-up roller, the rotation of the rotating shaft for the separation roller is transmitted to the frame member by the act of the bearing-type one-way clutch and the first collar as one-piece.
In the paper feeder, the second clutch member may include a spring-type one-way clutch that has a spring wound around outer surfaces of the first collar and the second collar. When the rotating shaft for the separation roller rotates in the direction to feed the documents in the document feeding direction, an inside diameter of the spring surrounding the first collar and the second collar, becomes smaller, the spring presses the outer surfaces of the first collar and the second collar and the first collar and the second collar act as one-piece. When the rotating shaft for the separation roller rotates opposite to the direction to feed the documents in the document feeding direction, with a torque less than the predetermined torque produced, the inside diameter of the spring surrounding the first collar and the second collar remains smaller, the spring presses the outer surfaces of the first collar and the second collar and the first collar and the second collar act as one-piece. When the rotating shaft for the separation roller rotates opposite to the direction to feed the documents in the document feeding direction, with the torque equal to or greater than the predetermined torque produced, the inside diameter of the spring surrounding the first collar and the second collar becomes larger than the outside diameters of the first collar and the second collar, and the first collar and the second collar act separately and independently.
When the rotating shaft for the separation roller rotates in the direction to feed the documents in the document feeding direction, the first collar and the second collar act as one-piece as the inside diameter of the spring surrounding the first collar and the second collar becomes smaller, so that the outer surfaces of the first collar and the second collar are pressed down. When the rotating shaft for the separation roller rotates opposite to the direction to feed the documents in the document feeding direction, with a torque less than the predetermined torque produced, the first collar and the second collar act as one-piece as the inside diameter of the spring surrounding the first collar and the second collar remains smaller, so that the outer surfaces of the first collar and the second collar are pressed down. When the rotating shaft for the separation roller rotates opposite to the direction to feed the documents in the document feeding direction, with the torque equal to or greater than the predetermined torque produced, the first collar and the second collar act separately and independently as the inside diameter of the spring surrounding the first collar and the second collar becomes larger than the outside diameters of the first collar and the second collar.
The paper feeder may further include a cover that covers the frame member, a cover protruding member that is disposed in the cover on a side of the frame member, and a frame protruding member that is formed on the frame member, upstream of the separation roller in the document feeding direction, and that lifts the frame member on a side of the pick-up roller by making the frame member rotate about the rotating shaft for the separation roller, with the frame protruding member, when the cover is closed.
As the cover is closed, the cover protruding member presses down the frame protruding member, so that the frame member turns about the rotating shaft for the separation roller so as to lift the pick-up roller.
In the paper feeder, the cover protruding member is formed of a plate spring.
Because the cover protruding member is formed of a plate spring, the cover protruding member may slide down toward the rotating shaft for the separation roller after the cover protruding member presses down the frame protruding member.